Heating – Advancing structure flexing – looping or coiling sheet – web... – Internally heated roll
Reexamination Certificate
2002-05-06
2003-02-11
Lu, Jiping (Department: 3749)
Heating
Advancing structure flexing, looping or coiling sheet, web...
Internally heated roll
C432S228000
Reexamination Certificate
active
06517346
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to fusing in electrostatography, and more particularly to an improved fusing station having an externally heated fuser roller for fixing a toner image to a receiver member.
BACKGROUND OF THE INVENTION
In electrostatographic imaging and recording processes such as electrophotographic reproduction, an electrostatic latent image is formed on a primary image-forming member such as a photoconductive surface and is developed with a thermoplastic toner powder to form a toner image. The toner image is thereafter transferred to a receiver member, e.g., a sheet of paper or plastic, and the toner image is subsequently fused or fixed to the receiver member in a fusing station using heat and/or pressure. The fusing station includes a fuser member which can be a roller, belt, or any surface having a suitable shape for fixing thermoplastic toner powder to the receiver member. The fusing step using a roller fuser member commonly includes passing the toned receiver member between a pair of engaged rollers that produce an area of pressure contact known as a fusing nip. In order to form the fusing nip, at least one of the rollers typically includes a compliant or conformable layer. Heat is transferred from at least one of the rollers to the toner in the fusing nip, causing the toner to partially melt and attach to the receiver member. In the case where the fuser member is a deformable heated roller, a resilient elastomeric layer is typically bonded to the core of the roller, with the roller having a smooth outer surface. Where the fuser member is in the form of a belt, e.g., a flexible endless belt that passes around the heated roller, it typically has a smooth outer surface which may also be hardened.
Simplex fusing stations attach toner to only one side of the receiver member at a time. In this type of station, the engaged roller that contacts the unfused toner is commonly known as the fuser roller and is a-heated roller. The roller that contacts the other side of the receiver member is known as the pressure roller and is usually unheated. Either or both rollers can have a compliant layer on or near the surface. It is common for one of these rollers to be driven rotatable by an external source while the other roller is rotated frictionally by the nip engagement.
It is known that a resilient fuser roller, when used in conjunction with a harder or relatively non-deformable pressure roller, e.g., in a Digimaster 9110 machine made by Heidelberg Digital LLC, provides easy release of a receiver member from the fuser roller, because the distorted shape of the compliant surface in the nip tends to bend the receiver member towards the relatively non-deformable unheated pressure roller and away from the much more deformable fuser roller. A pressure roller may advantageously be provided with a polymeric outermost coating, such as the pressure roller disclosed in the Chen et al. patent application (U.S. patent application Ser. No. 09/957,992, filed Sep. 21, 2001).
The most common type of fuser roller is internally heated, i.e., a source of heat is provided within the roller for fusing. Such a fuser roller generally has a hollow core, inside of which is located a source of heat, usually a lamp. Surrounding the core can be an elastomeric layer through which heat is conducted from the core to the surface, and the elastomeric layer typically contains fillers for enhanced thermal conductivity.
Less common is an externally heated fuser roller, such as for example used in an Image Source 120 copier marketed by Eastman Kodak Company, which fuser roller is typically heated by surface contact with one or more heating rollers. Externally heated fuser rollers are disclosed by the O'Leary patent (U.S. Pat. No. 5,450,183), the Derimiggio et al. patent (U.S. Pat. No. 4,984,027), the Stack et al. patent application (U.S. patent application Ser. No. 09/680,134, filed Oct. 4, 2000), and the Chen et al. patent application (U.S. patent application Ser. No. 09/680,138, filed Oct. 4, 2000).
A conventional toner fuser roller includes a rigid cylindrical core member, typically metallic such as aluminum, coated with one or more synthetic layers usually formulated with polymeric materials made from elastomers. A resilient base cushion layer, which may contain filler particles to improve mechanical strength and/or thermal conductivity, is typically formed on the surface of the core, which may advantageously be coated with a primer to improve adhesion of the resilient layer. Roller cushion layers are commonly made of silicone rubbers or silicone polymers such as, for example, polydimethylsiloxane (PDMS) polymers disclosed by the Chen et al. patents (U.S. Pat. Nos. 5,960,145 or 6,020,038).
Some roller fusers rely on film splitting of low viscosity oil to enable release of the toner and (hence) receiver member from the fuser roller. The oil is typically applied to the surface of the fuser from a donor roller coated with the oil provided from a supply sump. A donor roller is disclosed in the Chen et al. patent (U.S. Pat. No. 6,190,771) and in the Chen et al. patent application (U.S. patent application Ser. No. 09/960,661, filed Sep. 21, 2001).
Release oils (commonly referred to as fuser oils) are composed of, for example, polydimethylsiloxanes. When applied to the fuser roller surface to prevent the toner from adhering to the roller, fuser oils may, upon repeated use, interact with PDMS material included in the resilient layer(s) in the fuser roller, which in time can cause swelling, softening, and degradation of the roller. To prevent these deleterious effects caused by release oil, a thin barrier layer made of, for example, a cured fluoroelastomer and/or a silicone elastomer, is typically formed on the resilient cushion layer, as disclosed in the Davis et al. patent (U.S. Pat. No. 6,225,409).
To rival the photographic quality produced using silver halide technology, it is desirable that electrostatographic multicolor toner images have high gloss. To this end, it is desirable to provide a very smooth fusing member contacting the toner particles in the fusing station. A fuser roller having improved gloss characteristics is disclosed in the Chen et al. patent application (U.S. patent application Ser. No. 09/608,290, filed Jun. 30, 2000). A fluorocarbon thermoplastic random copolymer useful for making a gloss control coating on a fuser roller is disclosed in the Chen et al. patent application (U.S. patent application Ser. No. 09/609,561, filed Jun. 30, 2000).
In the fusing of the toner image to the receiver member, the area of contact of a conformable fuser roller with the toner-bearing surface of a receiver member sheet as it passes through the fusing nip is determined by the amount pressure exerted by the pressure roller and by the characteristics of the resilient cushion layer. The extent of the contact area helps establish the length of time that any given portion of the toner image will be in contact with and heated by the fuser roller.
As previously mentioned, PDMS cushion layers may include inorganic particulate fillers, such as for example made of metals, metal oxides, metal hydroxides, metal salts, and mixtures thereof. The Fitzgerald patent (U.S. Pat. No. 5,292,606) describes fuser roller base cushion layers that contain fillers of particulate zinc oxide and zinc oxide-aluminum oxide mixtures. Similarly, the Fitzgerald patent (U.S. Pat. No. 5,336,539) describes a fuser roller cushion layer containing dispersed nickel oxide particles. Also, the fuser roller described in the Fitzgerald et al. patent (U.S. Pat. No. 5,480,724) includes a base cushion layer containing 20 to 40 volume percent of dispersed tin oxide particles.
Filler particles may also be included in a barrier layer. For example, the Chen et al. patent (U.S. Pat. No. 5,464,698) discloses a toner fuser member having a silicone rubber cushion layer and an overlying barrier layer of a cured fluorocarbon polymer in which is dispersed a filler comprising a particulate mixture that includes tin oxide.
The Chen et al. patent
Aslam Muhammed
Chen Jiann-Hsing
Pavlisko Joseph
Wu Fangsheng
Kessler Lawrence P.
Lu Jiping
NexPress Solutions LLC
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